Extended-reach drilling technology has rapidly developed during the past three decades. It requires improved new models and technology. This study has created a rapid optimum method to design the horizontal well drilling parameters. Genetic Algorithm is applied in this method to optimize the parameters such WOB, RPM. According to practical situation, the suitable fitness function and value of operators of GA are given and reasonable convergence delay-independent conditions are set. Based on the intelligence and global quick search of GA and the convergence of GA, the design parameters can be globally optimized quickly and accurately. An example is taken to prove that the application of GA in the field of drilling parameters is successful. This optimization method based on GA can provide guide for field design.